The medical industry has become increasingly dependent upon the ability to measure various entities in physiological fluids in order to be able to determine the health status of an individual, dosage level for drugs, use of illegal drugs, genomic sequences, and the like. Thus, the capability of taking a physiological sample and rapidly analyzing for a particular component has made medical therapies more efficient and increasingly successful.
In many instances, one wishes to use blood as a source to diagnose a patients health or to monitor the efficacy of drugs that have been administered to the patient. Blood as a source for the determination of these parameters has many deficiencies. Among its deficiencies when used directly or even when diluted with buffer are: blood rapidly coagulates, blood contains a large number of light absorbing and florescent substances; blood exhibits variations in composition, its characteristics can change in relation to the reagents used in the assays; and blood exhibits variations in the presence or absence of oxygen. These properties complicate the use of blood as a sample for diagnostic purposes. Various techniques have been employed to avoid these problems; high dilution, addition of anticoagulants, separation of blood into plasma and its cellular components, and the like. During such manipulations, great care must be taken to avoid lysis of red blood cells to avoid the release of hemoglobin, which can interfere with diagnostic assays. Despite the problems associated with the use of blood as the sample medium, in many instances, blood is the only source which provides the information of interest. Therefore, identifying ways of using whole blood, while diminishing the interference from its constituents is highly desirable.
There is, therefore, substantial interest in devising new approaches for using and manipulating blood for diagnostic purposes. One area of particular interest is the assessment of platelet function. The role of platelets in mammalian physiology is extraordinarily diverse, but their primary role is in promoting thrombus formation. In many situations, one wishes to evaluate the ability of the blood to clot, a parameter that is frequently controlled by the ability of platelets to adhere and/or aggregate. Thus, one may wish to assess the adhesive functions of platelets. For example, one may wish to know whether to administer drugs that will block, or promote, clot formation, or one may need to detect deficiencies in platelet function prior to surgical procedures. In other instances one may be interested in evaluating the effectiveness of a platelet inhibitor that is being tested, as a new drug, or is being used as approved clinical treatment in a patient.